This invention is related to the delivery of expandable devices commonly called "stents" within a body lumen such as an artery and the expansion of the stent therein to maintain the patency of the body lumen. The invention is particularly suitable for the delivery of the stents after angioplasty procedures.
Percutaneous transluminal coronary angioplasty (PTCA) is now a widely practiced procedure for treating coronary artery disease. In a typical PTCA procedure, a dilatation catheter having an inflatable, relatively inelastic balloon on the distal end thereof is advanced through a patient's arterial system until the deflated balloon crosses an atherosclerotic lesion to be dilated. The balloon is inflated to a predetermined size with radiopaque liquid at relatively high pressures (e.g., up to 8 atmospheres or more) to compress the atherosclerotic plaque and to dilate the artery in the stenotic region. After dilation the balloon is then deflated so that the catheter can be removed. Due to the enlarged arterial passageway, increased blood flow results.
In typical PCTA procedures, a guiding catheter having a preformed distal end is first percutaneously introduced into the patient's arterial system and advanced until the distal tip of the catheter is disposed in the ostium of a coronary artery. A guide wire is slidably disposed within an inner lumen of a dilatation catheter and both are advanced through the guiding catheter to the distal end thereof. The guide wire is first advanced out of the distal tip of the dilatation catheter into the patient's coronary anatomy until the distal end of the guide wire crosses the lesion to be dilated. The physician usually shapes the distal end of the guide wire to facilitate steering through the patient's tortuous coronary arteries. Once the guide wire is in place, the dilatation catheter is advanced out of the distal tip of the guiding catheter over the guide wire until the deflated balloon on the distal end of the dilatation catheter is positioned across the lesion. The balloon is inflated to a suitable pressure to dilate the stenosis, deflated, and then removed from the patient's vasculature.
For a more detailed description of the angioplasty procedures and the devices used in such procedures, reference is made to U.S. Pat. No. 4,332,254 (Lundquist); U.S. Pat. No. 4,323,071 (Simpson-Robert); U.S. Pat. No. 4,439,185 (Lundquist); U.S. Pat. No. 4,468,224 (Enzmann et al.); U.S. Pat. No. 4,516,972 (Samson); U.S. Pat. No. 4,538,622 (Samson et al.); U.S. Pat. No. 4,554,929 (Samson et al.); U.S. Pat. No. 4,569,347 (Frisbie); U.S. Pat. No. 4,571,240 (Samson et al.); U.S. Pat. No. 4,616,652 (Simpson); U.S. Pat. No. 4,748,982 (Horzewski et al.); U.S. Pat. No. 5,300,085 (Yock); U.S. Pat. No. 5,496,346 (Horzewski et al.); and U.S. Pat. No. 5,626,600 (Horzewski et al.), which are hereby incorporated in their entirety by reference thereto.
On occasion, the inflation of the balloon during angioplasty causes a dissection in the arterial lining, e.g., the stenotic plaque or the arterial intima. When the balloon is deflated after such a dilation, blood can flow between the arterial wall and the dissected lining constricting the flow passage therein or causing a section of the dissected lining, commonly called a "flap," to be forced into the flow passageway thereby partially or completely blocking the blood flow through the artery.
Several methods have been proposed to resecure a dissected lining to the artery wall. For example, the dilatation catheter can be removed after the angioplasty procedure has been performed and replaced with a catheter having an expandable member at the distal end which allows for the perfusion of blood through the expandable member when expanded. In this method, the expanded member presses the dissected tissue lining against the arterial wall for an extended period until the dissected lining is re-secured to the arterial wall. Blood perfuses through the expanded member so that ischemic conditions are minimized or eliminated distal to the expanded member. However, these lining repair procedures usually require leaving the catheter with the expanded member in place for an extended period, e.g., fifteen minutes or more, in order to ensure that the lining has been properly re-secured to the arterial lining. Suitable catheters for this purpose are disclosed in U.S. Pat. No. 4,790,315; U.S. Pat. No. 4,998,539 (Delsanti); U.S. Pat. No. 5,034,001 (Garrison et al.); and U.S. Pat. No. 5,002,560 (Machold et al.), each of which is incorporated herein in their entirety by reference thereto.
Much development work has also been recently performed on the use of expandable stents in situations where long term expansion in an arterial or other bodily lumen is desired, such as in the instances described above. Expandable stents and their method of use are described in, for example, U.S. Pat. No. 5,603,721 (Lau et al.); U.S. Pat. No. 5,421,955 (Lau et al.); U.S. Pat. No. 5,514,154 (Lau et al.); U.S. Pat. No. 4,655,771 (Wallsten); U.S. Pat. No. 4,733,665 (Palmaz); U.S. Pat. No. 4,739,762 (Palmaz); U.S. Pat. No. 4,762,128 (Rosenbluth), Japanese application 57-89859 published Jun. 4, 1982, and European Application 0183372 published Jun. 9, 1986 which are hereby incorporated by reference.
More recent developments include stent delivery systems disclosed in U.S. Pat. No. 5,158,548 to Lau et al. Such a stent delivery system has an expandable stent in a contracted condition positioned on an expandable member, such as an inflatable balloon, disposed on the distal portion of an elongated catheter body. A guide wire extends through an inner lumen within the elongated catheter body and out its distal end. A tubular protective sheath is secured by its distal end to the portion of the guide wire which extends out ofthe distal end of the catheter body and fits over the stent mounted on the expandable member on the distal end of the catheter body.
Another stent delivery system is disclosed in U.S. Pat. No. 5,458,615 to Klemm et al. Such a delivery system includes an elongated delivery sheath and a catheter disposed within an outer lumen of the sheath having an expandable member on its distal extremity. An expandable stent is mounted on the expandable member of the catheter. The distal portion of the sheath tapers down and is tucked within an elastic cone during transport of the stent to a damaged region of the patient's body lumen. A manipulating device is provided on the proximal end of the delivery system to effect relative axial movement between the sheath and the catheter to expose the stent mounted on the expandable member to allow the expansion of the stent by the expansion of the expandable member.
Still another stent delivery system is disclosed in U.S. Pat. No. 5,634,928 to Fischell et al. This integrated catheter system uses a balloon angioplasty catheter placed through a central passageway of a stent delivery catheter to enable balloon angioplasty and stent delivery to be accomplished with a single device. The Lau et al., Klemm et al., and Fischell et al. patents are incorporated by reference herein in their entirety.
Some stent delivery systems use stent pushers to deploy the stent. An example of a stent pusher is shown in U.S. Pat. No. 4,580,568 to Gianturco. In this device, a stent is compressed to a reduced diameter which is several times smaller than its expanded diameter. The stent is positioned in a passageway in the vascular system by means of a sheath while the stent is retained in the compressed size. A flat-ended catheter/stent pusher is advanced through the sheath to hold the stent in place in the passageway while the sheath is withdrawn from the passageway allowing the stent to expand in the passageway into its expanded shape to hold the passageway open. This technology is also discussed in an article entitled "Tracheobronchial Tree: Expandable Metallic Stents Used In Experimental And Clinical Applications" by Gianturco et al., Radiology, vol. 158, pp. 309-12 (published Dec. 5, 1986). The Gianturco patent and article are incorporated by reference herein.
Despite these improvements, there is still a need for an improved stent delivery system that is capable of negotiating tortuous vessels and crossing a tight stenosis.